選択ソート
選択ソート時間の計算量: O ( n 2 ) O(n^2)O ( n2 )
コード上で直接
ジャバ:
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class SelectionSort {
private static List<Integer> selectionSort(List<Integer> arr) {
List<Integer> newArr = new ArrayList<>(arr.size());
int size = arr.size();
for (int i = 0; i < size; i++) {
int smallest = findSmallest(arr);
newArr.add(arr.get(smallest));
arr.remove(smallest);
}
return newArr;
}
private static int findSmallest(List<Integer> arr) {
int smallest = arr.get(0);
int smallestIndex = 0;
for (int i = 0; i < arr.size(); i++) {
if (arr.get(i) < smallest) {
smallest = arr.get(i);
smallestIndex = i;
}
}
return smallestIndex;
}
public static void main(String[] args) {
List<Integer> arr = new ArrayList<>(Arrays.asList(5, 3, 6, 2, 10));
System.out.println(selectionSort(arr)); //[2, 3, 5, 6, 10]
}
}
import java.util.Arrays;
public class SelectionSort2 {
// this version uses raw arrays instead of ArrayList
public static void selectionSort(int[] target) {
for (int i = 0; i < target.length - 1; i++) {
int left = target[i];
for (int j = i + 1; j < target.length; j++) {
int right = target[j];
if (left > right) {
target[i] = right;
target[j] = left;
left = right;
}
}
}
}
public static void main(String[] args) {
int[] arr = {
5, 3, 6, 2, 10};
selectionSort(arr);
System.out.println(Arrays.toString(arr)); // [2, 3, 5, 6, 10]
}
}
子：
#include <stdio.h>
#include <stdlib.h>
#define SIZE 5
// Finds the smallest value in an array
int findSmallest(int *arr) {
// Stores the smallest value
int smallest = arr[0];
// Stores the index of the smallest value
int smallest_index = 0;
for (int i = 1; i < SIZE; i++) {
if (arr[i] < smallest) {
smallest = arr[i];
smallest_index = i;
}
}
return smallest_index;
}
int *selectionSort(int *arr) {
// Create new Array
int *newArr = (int *)malloc(SIZE * sizeof(int));
for (int i = 0; i < SIZE; i++) {
int smallest = findSmallest(arr);
newArr[i] = arr[smallest];
// same as deleted by changing to the largest value
arr[smallest] = INT_MAX;
}
return newArr;
}
int main(void) {
int arr[SIZE] = {
5, 3, 6, 2, 10};
int *sortarr = selectionSort(arr);
// print result
for (int i = 0; i < SIZE; i++) {
printf("%d ", sortarr[i]);
}
return 0;
}
C++：
#include <iostream>
#include <vector>
using std::cout;
using std::endl;
// Finds the smallest value in an array
template <typename T>
int find_smallest(const std::vector<T>& arr) {
// stores smallest value
T smallest = arr[0];
// stores index of the smallest value
int smallest_index = 0;
for (int i = 0; i < arr.size(); i++) {
if (arr[i] < smallest) {
smallest = arr[i];
smallest_index = i;
}
}
return smallest_index;
}
template <typename T>
std::vector<T> selection_sort(std::vector<T> arr) {
std::vector<T> sorted;
while(!arr.empty()) {
// find smallest element and add it to sorted array
int smallest_index = find_smallest(arr);
sorted.push_back(arr[smallest_index]);
// remove smallest element from non-sorted array
arr.erase(arr.begin() + smallest_index);
}
return sorted;
}
int main() {
std::vector<float> arr = {
1.2, 1.0, 3, 0, -1, 0.5, 100, -99};
std::vector<float> sorted = selection_sort(arr);
cout << "Sorted array: ";
for (float num : sorted) {
cout << num << " ";
}
cout << endl;
}
パイソン：
# Finds the smallest value in an array
def findSmallest(arr):
# Stores the smallest value
smallest = arr[0]
# Stores the index of the smallest value
smallest_index = 0
for i in range(1, len(arr)):
if arr[i] < smallest:
smallest_index = i
smallest = arr[i]
return smallest_index
# Sort array
def selectionSort(arr):
newArr = []
for i in range(len(arr)):
# Finds the smallest element in the array and adds it to the new array
smallest = findSmallest(arr)
newArr.append(arr.pop(smallest))
return newArr
print(selectionSort([5, 3, 6, 2, 10]))